Electrical and electronic components such as connectors have recently been undergoing dramatic increases in performance. This trend is especially striking in connectors used in surface-mount technology (SMT), where molding materials with high flame retardance, high flowability, high melt stability, high mechanical properties, and a high reflow heat temperature resistance are required.
Thermoplastic resins which have hitherto been used to mold SMT connectors include aromatic polyamides, polytetra-methylene adipamide, a polymer of tetramethylene diamine and adipic acid ("nylon 46"), polyphenylene sulfide and liquid crystal polymers. However, in the case of aromatic polyamides and nylon 46, it is generally necessary to carry out flame-retarding treatment in order to achieve the high flame retardance required, which means attaining a UL 94 rating of V-0. Various methods exist for carrying out flame-retarding treatment, although polyamides are generally flame-retarded by a method involving the addition of a flame retardant. However, when a low-molecular-weight flame retardant is used and a flowability enhancer such as a wax is also added to elicit a high flowability, the mechanical properties intrinsic to the polyamide are lost. Also, the reflow heat temperature resistance decreases by adding a low-molecular-weight flame retardant. Therefore, polyamide resin compositions endowed with the high flame retardance, high flowability, high melt stability, high functional properties, and high reflow heat temperature resistance required of SMT connector molding materials have yet to achieved.
The use of epoxy group-containing compounds, such as glycidyl isocyanurate and novolak-epoxy resins, as binders in paints is well known, but these compounds have not often been used as additives for enhancing the properties of resins. One case in which they have been used as resin additives is in methods for the stabilization of flame-retarded resin compositions characterized by the use of glycidyl isocyanurate, either alone or in combination with other compounds, as the heat stabilizer in resin composites of styrene resin and carbonate resins that have been flame-retarded using brominated flame retardants (Japanese Unexamined Patent Application Disclosure [Kokai] Nos. 2-279,763 (1990) and 4-266,956 (1992)). However, because general-purpose resin composites of styrene and carbonate resins such as this have a heat resistance that is far inferior to that of polyamides, they cannot be used as the molding materials for electrical and electronic components such as SMT connectors.